How to make it

Preheat oven to 350°F. Coat a 9-inch pie pan with cooking spray.

To prepare crust: Process 32 wafers, confectioners' sugar, oil, milk and butter in a food processor until finely ground. Press the mixture into the bottom and up the sides of the prepared pan, creating an even, dense crust. Bake for 12 minutes. Cool on a wire rack to room temperature, about 1 hour, pressing any puffed parts of the crust back into the pan.

To prepare filling: Meanwhile, puree raspberries, lemon juice and salt in a blender or food processor until smooth. Strain through a fine-mesh sieve into a medium bowl, pressing with a rubber spatula to extract the juice; discard seeds.

Bring 1 inch of water to a slow simmer in a large saucepan. Combine egg whites, granulated sugar and cream of tartar in a 3-quart stainless-steel bowl. Beat with an electric mixer on medium speed until foamy. Set the bowl over the simmering water and continue to beat on medium speed, moving the mixer around, until the mixture is glossy and thick, about 3 1/2 minutes. Increase the speed to high, and continue beating over the simmering water until very stiff and glossy, about 3 1/2 minutes more (the eggs will be at a safe temperature, 160°F, at this point). Remove from the heat (be careful of the escaping steam) and continue beating on medium speed until room temperature, 3 to 5 minutes.

Fold the raspberry puree into the meringue until combined. Pour the raspberry filling into the pie crust; crumble the remaining chocolate wafer over the top. Place the pie on a level surface in your freezer and freeze until solid, at least 6 hours. To serve, let the pie stand at room temperature until softened slightly, about 10 minutes, before slicing.